The same has happened to my coin also. Mine has definitely deteriorated over time, I suspected it was to do with the holder they were housed in. I briefly spoke to Casascius about it and he is aware of it.

I believe it is toning from a chemical in the holders they were distributed in.

Small sampling, but I had 4 from original issue - 2 i sent for grading immediately, 2 I kept in the original slab. The two in the original slab toned on the rims exactly like these photos.

Interesting side note, I sent the two slightly toned ones to ANACS for grading after they had the toning developed on the rim and they came back MS67 DCAM and MS65 DCAM. In the normal coin world toning can add value or hurt value depending on eye appeal.

Edit to add: DO NOT TRY TO CLEAN. Just remove from holder and either send to ANACS or put in airtite.

Thanks for the info everyone. Even if I don't sell them, at least I know to get them out of the cases they are currently in. Anyone know where to buy airtights that will fit these coins? I'm assuming they are the same dimensions as the original silver Casascius coins, but I don't have any of those so I don't know for sure.

Hmmm, I should check up on my Bitcoin Bowl coin and see if it has any tarnish. If not I should probably get it graded ASAP or at least move it into an airtite. I didn't know that the original holder would cause this issue (which is quite annoying IMO).

Bad idea of removing coins from holder if you do not have experience. Do not touch with bare hands ! It is better to leave as it is or sends to ANACS. I would like to buy in the original packaging. PM

I handle coins with bare hands all of the time. You can safely hold them by the rim with a few steps beforehand. Step 1 Wash your hands really well.Step 2 Only hold them over a soft towel - I have dropped several Cas coins with no damage and yes they still graded well.

Cotton gloves are bad to use - they leave little lint balls and give you a better chance of dropping the coin.Never read up on nitrile gloves...I have seen some people here using them.

When I crack a slab or open an air-tite I just left the coin fall onto a microfiber towel...then grab it with my hands. Coins are strong and do not ding easy it is really just finger prints that cause the real damage or wiping them.

I have two Bitcoin Bowl Coins that I'm looking to sell. Images are here:

Coin 1, Front:

Coin 1, Back:

Coin 2, Front:

Coin 2, Back:

They're not graded, but they are in the original packaging and I've never taken them out or handled them.

I'm asking 0.4 BTC each.

I'll do escrow if buyer pays and we can agree on who to use. Shipping will be calculated based upon the shipping location and paid by the buyer. Continental US buyers only.

I had not heard of these. Can you supply more details? Do they have holograms/are they loaded? (can't see any). Do you know how many were produced? If you do sell and the buyer is ok with it, can you let me know the sale price and I will add to the big list. Thanks!

"There is only one thing that is seriously morally wrong with the world, and that is politics. By 'politics' I mean all that, and only what, involves the State." Jan Lester "Escape from Leviathan"

I had not heard of these. Can you supply more details? Do they have holograms/are they loaded? (can't see any). Do you know how many were produced? If you do sell and the buyer is ok with it, can you let me know the sale price and I will add to the big list. Thanks!

They are fairly well known to most Casascius collectors and they do not have a hologram or private keys. I think it is the only silver coin Mike has made since he was prevented from selling loaded ones. The mintage of these St Petersburg coins is 2,000 - however over half of these were scrapped because he was not happy with the quality.